The nsjail build has been broken since the 3.7.5 bison bump:
/nix/store/(...)/bin/ld: kafel/libkafel.a(libkafel.o):
in function `kafel_yyerror':
arm_syscalls.c:(.text+0x6833): undefined reference to `YYUSE'
The issue is coming from kafel and has been fixed upstream. More infos
at: https://github.com/google/kafel/pull/28.
Kafel being distributed through a git submodule in the nsjail repo, we
can't directly fetchpatch the fix from Github. We had to manually
modify the said patch to add a /kafel prefix.
We'll need to remove this patch for the next nsjail version bump.
a9a112e57f